Before, Unity was divided into two versions, a free version and a pro version. The free version was good enough for most smaller games that didn't require advanced graphics settings. The fully featured pro version costed $1500(or $75 a month) was pretty steep for compared to Unreal's old $19 a month offering.
To stay competitive, Unity is letting developers use all of their engine features for free if they make under $100,000. If your game ends up being a massive success, this could end up being a better deal financially then Epic's 5% cut.
The workflows on these engines are completely different, but both are powerful enough to make any types of games. At the end of the day it may just come down to preference.
This article was written by Steven Yang. Follow him on Twitter